1. Field of Invention
The present invention relates to a multi-layer printed circuit antenna in which a screen printing technology is used to deposit the conducting material forming the circuit layout directly on a low-cost dielectric material. The dielectric material used may be a thin layer supported by low-loss, foam-like material for spacing between antenna layers, or a thick, high-density, low-loss dielectric material acting as both the printing surface and the spacer between the antenna layers. The use of a thick dielectric eliminates the need to produce and apply one layer of the foam-like material for every printed circuit.
The use of a screen printing, or an additive process, is less expensive than an etching process or a subtractive counterpart, due to the particular steps in the process itself, and the lower cost of materials.
2. Related Art
Flat plate antennas using multi-layer printed circuit designs have been available as a consumer product for over a decade for DBS systems or direct to home TV systems (DTH/TV). They also have applications in MMDS, LMDS and other wireless communications links. The size of such antennas depends on the application, but it may range from 6 inches square to 30 inches square, with one set of continuous layers. The size can be larger for coplanar layers connected with a power combining network. The shape of the planar aperture can be square, rectangle, or other arbitrary shape.
Among the key elements in antenna costs are the materials and processing costs. Typically, the cost of an antenna is dependent on its size. The size of the antenna also determines the antenna losses and aperture efficiency. Improving the material characteristics of the antenna will lower the losses and allow for reduction of antenna size for the same performance, which in turn reduces the cost.
Competing designs to the multi-layer flat plate antenna include the conventional reflector system and waveguide-based flat plate antennas. The conventional reflector system antenna is lower in cost, mainly because of the large volume of production that it enjoys. However, the multi-layer flat plate antenna can be cost competitive against the conventional reflector system antenna for smaller size designs, even at low volume production.
The waveguide-based flat plate designs use metal structures or metal-coated plastic structures. Both the metal and metal-coated plastic structures are more expensive to manufacture than a multi-layer flat plate antenna. The metal-coated plastic structures used in waveguide-based flat plate antennas sometimes also have temperature stability and reliability problems. Thus, the multi-layer flat plate antenna is superior to the conventional waveguide-based flat plate antenna.
A multi-layer flat plate antenna is illustrated in FIG. 1. The antenna comprises a ground plane 1, and a strip-line power distribution circuit 2 which feeds an array of printed or punched radiating elements 3. The radiating elements 3 can be slots, patches or other forms of apertures and are formed in a layer of dielectric material 7. The radiating elements 3 can also be punched or formed on a planar metal plate. The radiating elements 3 and dielectric material 7, function as the upper ground plane for the strip-line structure of the feeding circuit, power distribution circuit 2. The strip-line power distribution circuit 2, as shown in FIG. 1, is formed on a thin dielectric material layer 6 and supported on either side with foam-like material, forming foam layers 4 and 5.
The conventional way of constructing the antenna of FIG. 1 is to use a copper-clad Mylar or similar conducting-material-coated thin dielectric for forming the power distribution circuit 2, and in some cases, also for the radiating elements 3. A mask is made for the power distribution circuit, and in some cases, for the printed radiating elements, and is used to chemically etch away the unwanted metal of the metal-coated layer, leaving only the printed power distribution circuit or printed radiating elements.
FIG. 2 is a diagram illustrating unwanted metal being etched away from a metal-coated layer. However, one problem with producing an antenna using the etching process, is that the etching process is expensive compared to a screen-printing process. Another problem is that both the circuit dielectric material 6 and 7, and the supporting foam-like material 4 and 5, contribute to the losses of the circuit and, consequently, adversely affect the antenna gain and efficiency.
It is an object of the present invention to overcome the foregoing problems. In particular, it is an object of the present invention to replace the etching process of the relatively expensive metal-coated dielectric layer by screen printing directly on a less expensive dielectric layer.
It is a further object of the present invention to provide an antenna, and a method for manufacturing an antenna, which uses direct screen printing on a less expensive, clear dielectric layer, as opposed to etching conducting material from a more expensive, copper-coated dielectric material.
It is another object of the invention to provide an antenna, and a method for manufacturing an antenna, in which screen-printing is conducted directly on a thick, low-loss dielectric material, thus eliminating the support layers between printed circuit layers, and providing rigidity to the overall structure.
Yet another object of the invention is to provide an antenna, and a method for manufacturing an antenna, wherein the conductivity is increased, and consequently a higher gain and higher efficiency antenna is produced by combining the screen-printing technique with a post-processing step of compressing the screen-printed layers of the multi-layer flat antenna.
An additional object of the invention is to provide an antenna, and a method for manufacturing an antenna wherein the conductivity is increased, and consequently a higher gain and higher efficiency antenna is produced by combining the screen-printing technique with a post-processing step of depositing a highly conductive paste or electroplating a highly conductive material on the screen-printed circuits and ground plane area of the antenna.
These and other objects may be achieved in accordance with the present invention.